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Lake on the 79N Glacier is splitting the ice - leaving permanent changes
https://www.awi.de/en/about-us/service/press/single-view/see-auf-dem-79n-gletscher-spaltet-das-eis-und-hinterlaesst-dauerhafte-veraenderungen.html14. August 2025 | Press release
Lake on the 79°N Glacier is splitting the ice – leaving permanent changes
A new AWI study shows that an approximately 21 square kilometre meltwater lake has caused gigantic cracks in the ice and that the water flowing off is lifting the glacier
Since the mid-1990s, the Greenland ice sheet has been losing mass, leaving only three floating tongues remaining. One of these, Nioghalvfjerdsbræ or the 79°N Glacier, is already showing the first signs of instability. In addition to the warm ocean water, which is increasingly thinning the ice from below, the runoff of meltwater on the surface is also playing an increasingly significant role. In a new study, researchers from the Alfred Wegener Institute investigated how - caused by global warming - a 21 km² large meltwater lake formed and developed on the surface of the 79°N Glacier. They observed that over the years, this lake has caused gigantic cracks and the outflowing water is lifting the glacier. Their findings have been published in the journal The Cryosphere.
The lake first appeared in the observation data of the year 1995. "There were no lakes in this area of the 79°N Glacier before the rise in atmospheric temperatures in the mid-1990s," as Prof. Angelika Humbert, glaciologist at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) stated. "From the time of its formation in 1995 until 2023, the lake's water repeatedly and abruptly drained through channels and cracks in the ice, causing massive amounts of fresh water to reach the edge of the glacier tongue towards the ocean." There were a total of seven such drainage events, four of which took place in the last five years.
"During these drainages, extensive triangular fracture fields with cracks in the ice formed from 2019 onwards, which are shaped differently from all lake drainages I have seen so far," Angelika Humbert marvels. Some of these cracks form channels with openings several dozen metres wide (moulins). Water flows through these moulins also after the main drainage of the lake, meaning that within hours, a huge amount of water reaches the base of the ice sheet. "For the first time, we have now measured the channels that form in the ice during drainage and how they change over the years."
After the lake had formed in 1995, its size decreased over time with the first cracks appearing. In recent years, the drainage has occurred at increasingly shorter intervals. "We suspect that this is due to the triangular moulins that have been reactivated repeatedly over the years since 2019," says Angelika Humbert. The material behaviour of the glacier plays a role here: on the one hand, the ice behaves like an extremely thick (viscous) fluid that flows slowly over the substrate. At the same time, however, it is also elastic, allowing it to deform and return to its original shape, similar to a rubber band. The elastic nature of the ice is what allows cracks and channels to form in the first place. On the other hand, the creeping nature of the ice helps channels inside the glacier to close again over time after the drainage has taken place. "The size of the triangular moulin fractures on the surface remains unchanged for several years. Radar images show that although they change over time inside the glacier, they are still detectable years after their formation." This data also reveals that there is a network of cracks and channels, meaning that there is more than one way for the water to escape.
…
Humbert, A., Helm, V., Zeising, O., Neckel, N., Braun, M. H., Khan, S. A., Rückamp, M., Steeb, H., Sohn, J., Bohnen, M., and Müller, R.: Insights into supraglacial lake drainage dynamics: triangular fracture formation, reactivation and long-lasting englacial features, The Cryosphere, 19, 3009–3032, https://doi.org/10.5194/tc-19-3009-2025, 2025.Lake on the 79°N Glacier is splitting the ice – leaving permanent changes
A new AWI study shows that an approximately 21 square kilometre meltwater lake has caused gigantic cracks in the ice and that the water flowing off is lifting the glacier
Since the mid-1990s, the Greenland ice sheet has been losing mass, leaving only three floating tongues remaining. One of these, Nioghalvfjerdsbræ or the 79°N Glacier, is already showing the first signs of instability. In addition to the warm ocean water, which is increasingly thinning the ice from below, the runoff of meltwater on the surface is also playing an increasingly significant role. In a new study, researchers from the Alfred Wegener Institute investigated how - caused by global warming - a 21 km² large meltwater lake formed and developed on the surface of the 79°N Glacier. They observed that over the years, this lake has caused gigantic cracks and the outflowing water is lifting the glacier. Their findings have been published in the journal The Cryosphere.
The lake first appeared in the observation data of the year 1995. "There were no lakes in this area of the 79°N Glacier before the rise in atmospheric temperatures in the mid-1990s," as Prof. Angelika Humbert, glaciologist at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) stated. "From the time of its formation in 1995 until 2023, the lake's water repeatedly and abruptly drained through channels and cracks in the ice, causing massive amounts of fresh water to reach the edge of the glacier tongue towards the ocean." There were a total of seven such drainage events, four of which took place in the last five years.
"During these drainages, extensive triangular fracture fields with cracks in the ice formed from 2019 onwards, which are shaped differently from all lake drainages I have seen so far," Angelika Humbert marvels. Some of these cracks form channels with openings several dozen metres wide (moulins). Water flows through these moulins also after the main drainage of the lake, meaning that within hours, a huge amount of water reaches the base of the ice sheet. "For the first time, we have now measured the channels that form in the ice during drainage and how they change over the years."
After the lake had formed in 1995, its size decreased over time with the first cracks appearing. In recent years, the drainage has occurred at increasingly shorter intervals. "We suspect that this is due to the triangular moulins that have been reactivated repeatedly over the years since 2019," says Angelika Humbert. The material behaviour of the glacier plays a role here: on the one hand, the ice behaves like an extremely thick (viscous) fluid that flows slowly over the substrate. At the same time, however, it is also elastic, allowing it to deform and return to its original shape, similar to a rubber band. The elastic nature of the ice is what allows cracks and channels to form in the first place. On the other hand, the creeping nature of the ice helps channels inside the glacier to close again over time after the drainage has taken place. "The size of the triangular moulin fractures on the surface remains unchanged for several years. Radar images show that although they change over time inside the glacier, they are still detectable years after their formation." This data also reveals that there is a network of cracks and channels, meaning that there is more than one way for the water to escape.
…